The system of the present invention is particularly suitable for use with capillary watering systems and systems of the type described in my copending Australian Provisional Patent Application PO 3891 entitled "Liquid supply apparatus and process" filed on Nov. 29, 1996, the contents of which are hereby incorporated herein by reference.
Numerous different types of plants are grown, stored, transported and distributed in plant containers arranged in trays. Although the eventual purchaser may purchase only one or a small number of plants in the plant containers, the growing, storing and distributing of large quantities of identical plants in this manner enables the plant grower to take advantage of economies of scale. The plant containers used may be circular or approximately square or rectangular in shape, allowing for efficient packing on trays.
If the trays are of a size which accommodates exactly a predetermined number of plant containers, the plant containers can be held in place in a relatively stable manner, abutting up against each other, and making it unlikely that the plant containers will be knocked or blown over. However, there is sometimes a requirement to hold plant containers of different sizes on the same tray, and sometimes the space taken up by the plant containers on the tray does not exactly match the available space on the tray. As plants grow, it is frequently necessary to provide greater spacing between them. This is typically done by removing every second plant container from the tray. However, this, and each other type of spacing irregularity, means that each plant container is no longer supported by abutment against its neighbouring containers, with the result that the plant containers can, and frequently do, get knocked over by wind or movement.
One type of system which avoids problems associated with individual plant containers falling over consists of a specially shaped vacuum formed holder with individual compartments for individual plant containers. These vacuum formed container trays are sometimes referred to as "scuttle trays", and consist of a structure with several spaced-apart well-shaped indentations. Each well-shaped indentation corresponds with the shape of a plant container which is inserted into it. An advantage of these vacuum formed trays is that they allow precise relative positioning of plants and automated treatment processes such as soil filling, planting and watering. However, a vacuum formed tray of this sort is in general suitable only for particular types of plants, as the spacing between individual plant containers is fixed by the configuration of the tray structure. Moreover, the vacuum formed tray is suitable in general terms only for smaller types of plant containers.
Another type of plant holder is a rack provided for plant containers placed on capillary matting or sand beds. A sand bed is a method for automatically watering plants in containers. The sand bed is filled to the top of the level of the sand with water, and plant containers with holes in or near their bottoms are placed on the sand, so that water can filter up through the soil in the plant containers to the plants.
A typical rack holding system for plant containers on sand beds consists of a lattice-like framework oriented horizontally and held several centimetres above the level of the sand bed by means of legs. Each of the holes in the lattice accommodates snugly a plant container, so that the bottom of the plant container touches the sand bed and the sides of the plant container are held against falling over by the lattice. However, the lattice arrangement does not allow for variable spacing between plant containers. A plant container can be placed in every lattice hole, but this may result in plants being too close together as they grow up. To create more space for each plant container, every second container can be removed; however, this may result in inefficient use of area if the necessary separation between adjacent plants is not a full container width.